The present invention relates to a safety ski binding comprising a plate or other similar member adapted to act as a support for the ski boot, which is mounted permanently on the ski and adapted to revolve about an axis perpendicular to the top surface of the ski.
The main advantage of this type of binding in comparison with the most popular conventional ski bindings comprising a toe abutment device or mechanism and a heel hold-down device or mechanism is that no sliding frictional contact takes place between the ski boot and the ski when the former rotates in relation to the latter. In fact, when a torsion stress is applied to the skier's leg the plate moves bodily with the boot. Moreover, it is easier to mount a binding of this type on a ski than a toe-end abutment device and heel hold-down device assembly, since only the plate pivot pin has to be secured to the ski.
The movable plate thus contemplated in ski bindings of this type comprises boot retaining means so arranged that the boot is released in case of forward or backward fall. On the other hand, resilient means are provided for constantly urging the movable plate to its normal position on the ski, these resilient means being adapted to permit the rotation of the plate when a torsion stress is exerted on the skier's leg. With this arrangement, a double safety is obtained: on the one hand in case of torsion, and on the other hand in case of forward or backward fall.
Certain known ski bindings of this general character are so designed that the rotation of the plate as a consequence of a torsion movement of the skier's leg is also attended by the movement of the boot retaining means towards their position corresponding to the release of the boot. This is observed notably in the case of the safety ski binding described in applicant's U.S. Pat. No. 3,647,235. In fact, in this patent, a single resilient member holds the rotary plate in its normal, operative position while controlling a jaw gripping the toe end of the boot, the arrangement being such that this jaw can rotate freely to release the boot when the plate has accomplished a predetermined angular movement.
The applicant's U.S. Pat. No. 3,966,218 of June 29, 1976, discloses another safety ski binding of the same general type, which comprises a toe end jaw adapted to slide on the rotary plate. In this case the arrangement is such that when the rotary plate has been moved angularly through a predetermined angle, the jaw supporting slide is unlocked so that the jaw will release the boot instantaneously.
However, in these two safety bindings there is no interaction between the boot retaining means normally counteracting the lifting thereof in case of forward or backward fall, on the other hand, and the retaining means normally counteracting a rotation due to torsion stress, on the other hand. In fact, the rotational movement of the plate has no effect on the heel hold-down means.
Now, this interaction would obviously be extremely desirable from the point of view of safety. In fact, in case of a complex fall, i.e. a fall combining a torsion stress and a traction effort, the tibia bone is considerably more vulnerable than in case of a simple fall. Therefore, when the skier is in a position of want of balance either forwards or backwards, a lateral stress weaker than that required when he is in a normal position is sufficient for breaking his tibia.
However, an interaction of this type is well known in conventional safety ski bindings, notably in the case of heel hold-down devices wherein the jaw can pivot both about a vertical axis to permit the lateral release of the boot and about a horizontal transverse axis to permit the vertical release of the boot. Heel hold-down devices of this type are known wherein the means for locking the jaw in both lateral and vertical directions are operatively interconnected so that unlocking one means entails a reduction in the locking effort exerted by the other, and vice versa.
It is also known through the German patent appln. DT-OS No. 2,504,281 to construct a binding in such a manner that an interaction occurs between a rotatable boot-supporting plate and a member provided on said plate for retaining the boot against lifting movements. For instance, in the form of embodiment illustrated in FIG. 3 of this last-mentioned patent, the heel hold-down member is connected to the rotary plate in such a manner that rotation of the latter is attended by the pivotal movement of the retaining member towards its release position.
Under these conditions, the release of the ski boot by lifting same is facilitated when the plate has already been caused to rotate as a consequence of a torsion stress exerted on the skier's leg.
However, one may question the real efficiency of this retaining member, namely a conventional heel hold-down device, for ensuring a stable centering of the plate as well as a proper elastic resistance of this plate during its rotation. In fact, the spring incorporated in the heel hold-down device and constituting the means for applying a return torque to the plate in order to center the latter, is disposed substantially vertically and therefore parallel to the axis of said torque. Moreover, the necessary return torque is transmitted from the spring to the plate by a connecting member such as a cable passing in a guide member rigid with the ski. This transmission member is therefore uncovered and therefore liable to become embedded in snow or ice, a fact most likely to interfere detrimentally with its operation or even lock it completely, thus jeopardizing the skier's safety.
In another French patent appln No. 7,416,349 (published under No. 2,228,510) there is disclosed a ski binding comprising two resiliently interconnected plates; one plate is secured to the ski and the other plate is connected to the one plate and movable relatively thereto.
The upper plate can perform oscillations of reduced amplitude about an axis perpendicular to the ski surface to generate a signal controlling the opening of the toe end and/or heel end jaws.
Therefore, the upper plate cannot move with the boot during its rotation, so that substantial friction occurs between the boot and the plate. Moreover, if a small-amplitude movement of the upper plate succeeds in actually releasing the lateral hook means, the retaining force on the other hand remains unchanged during a forward fall causing the opening of said lateral hooks, due to the particular nature of the resilient means interconnecting the two plates.
It is the essential object of the present invention to provide a safety ski binding of the general type set forth hereinabove which is at the same time reliable, safe, compact and has a good aesthetic appearance.
The ski binding according to this invention comprises a ski boot supporting member adapted to rotate about an axis perpendicular to the ski surface and provided with at least one boot hooking member mounted on said support for movement between a normal operative position in which said retaining member cooperates with a member rigid with the boot so as to hold the latter against movement on said support, and an inoperative position to which said hooking member is moved when an abnormal load is applied to the skier's leg and said boot is released in relation to said support, resilient means being provided for urging on the one hand said support to its normal position on the ski and on the other hand said hooking member to its operative position.
However, for obtaining the desired result, the boot supporting member has the shape of a flat case formed of either a single compartment or two compartments containing the component elements of a resilient system operative both between said case and a fixed element, on the one hand, and between this case and the hooking member, on the other hand; in addition, a kinematic chain is provided between said case, said hooking member and said resilient system, whereby a movement of rotation of said case tending to move the latter away from its normal position is attended by the release of the force urging said boot hooking member to its operative position, and inversely, when said hooking member is moved towards its inoperative position the force holding the pivoting case against rotation is also released.
It may be noted that only the hooking means is located externally of the case, so that the risks previously mentioned and those due to weather conditions (snow and ice) are reduced very considerably. Due to its particular conception, the ski binding according to the present invention constitutes a reliable, compact and aesthetical device.
In a specific form of embodiment of the present invention, the resilient system comprises one or a plurality of springs acting on the one hand on a cam provided on the fixed pivot pin of the pivoting case, so as to hold and return the latter in and to its normal position, and on the other hand on a cam associated with the boot hooking means, the arrangement being such that the rotation of the case is attended by a decrease in the pressure exerted by said springs on the cam associated with the hooking means, and that conversely the movement of this hooking means towards its inoperative position is attended by a reduction in the pressure exerted by the springs on the pivot cam.
The case is pivoted on a central fixed pivot pin adapted to be fastened to the ski, the movable boot hooking means co-acting with a first piston slidably mounted in the case and urged by resilient means both against the movable boot retaining member in order to resiliently hold the latter in its operative position and against a flat cam provided on the fixed pivot of the case, so as to resiliently hold the case against rotation in its normal position.
In a preferred form of embodiment, the movable hooking means comprises a pair of hooks disposed laterally on the pivoting case on either side of the fixed pivot pin disposed in the central area of the case, and each hook aforesaid includes a ramp adapted to co-act with the corresponding end portion of a spindle passing through a piston and projecting from the case, and the resilient device urging the piston against the hooks and the pivot cam consists of at least one spring reacting against the relevant end of the case, the pivoting hooks being adapted to bear against retaining means rigid with the boot.
According to another form of embodiment, the binding is provided with a single boot hooking means movable between an operative boot-retaining position and an inoperative boot-releasing position, and with a complementary fixed boot hooking means rigid with the boot supporting case.
With this arrangement, only one piston may be provided for urging the movable boot hooking means to its closed position and holding the case against rotation, together with a second piston having only the function of holding the case against rotation. Thus, when the movable boot hooking means is moved, the first piston cannot continue to hold the case against rotation, but on the other hand the second piston, independent of said movable boot hooking means, continues to exert a return torque tending to hold the movable boot hooking means against rotation.
Thus, the binding is simplified considerably.
In other improved forms of embodiment, the present invention also contemplates of further simplifying the above-summarized structures, notably the last-mentioned ones comprising two resilient systems each associated with a piston.
For this purpose, according to another form of embodiment, the case encloses a single resilient system urging the two pistons housed in the case against a pair of cams formed on the opposite faces of a fixed central pivot pin about which the case is adapted to rotate, one of said pistons co-acting with a boot hooking means movable between an operative boot-retaining position and an inoperative release position, and said resilient system and said pair of pistons are so disposed that, in case of front fall of the skier, only the first piston rigid with the movable hooking means moves away from the corresponding cam, the second piston remaining in close engagement with the fixed pivot while maintaining a torque retaining the case in a position of engagement with the ski surface.
With this arrangement, the number of component elements necessary for making the ski binding is reduced considerably while freeing a volume available along about one-half of the case length.
However, many modifications and changes may be brought to the safety ski binding according to the present invention of which several forms of embodiment are shown in the accompanying drawings.